1. Field of the Invention
This invention relates to a minicomputer system and more particularly to an arithmetic control unit integrated on a one-chip semiconductor device.
2. Description of the Prior Art
The present development of semiconductor process technology has brought forth a LSI of 5000 gates at maximum on a one-chip semiconductor (MOS) device. However, it is sufficient to provide a microprocessor including functions of 8-bit or at most 12-bit logic operation for a desk-top type calculator, an industrial controller with simplified construction and the like. A restriction results from the number of pins or output terminals led out of the one-chip semiconductor device and the chip size thereof. This causes communication channels with utilization devices and a capability of a logic unit, for example, register bit-lengths, to be restricted. This in turn causes the number of functional elements contained in the microprocessor to be restricted. Therefore, it is difficult for the microprocessor integrated on a one-chip semiconductor device to have substantially the same performance as the processor of a conventional mini-computer.